Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.53	3.379%	$216.61	$216.61	$216.60	$216.60
Purchase #2	$62.50	8.679%	$67.9244	$67.92	$67.90	$67.90
Purchase #3	$215.27	6.698%	$229.6888	$229.69	$229.70	$229.70
Purchase #4	$18.38	8.763%	$19.9906	$19.99	$20.00	$20.00
Purchase #5	$102.60	8.370%	$111.1876	$111.19	$111.20	$111.20
Purchase #6	$223.82	13.213%	$253.3933	$253.39	$253.40	$253.40
Purchase #7	$174.27	9.639%	$191.0679	$191.07	$191.05	$191.10
7 purchase totals =	$1,006.37		$1,089.8626	$1,089.86	$1,089.85	$1,089.90